In recent years, many large circulation periodicals have appeared which require rapid handling of portions of the periodicals consisting of signatures which are gathered for stitching, trimmed, bundled for minimum shipping costs, and shipped. A typical operation utilizes a multitude of packer boxes each of which receives signatures seriatum from a signature supply means, opens each signature, and drops the signatures successively straddling a gathering chain that runs in front of the packer boxes and carries the complete collection of gathered signatures to the stitcher. Moreover, because of the need for highly efficient plant operations, there has been a constant effort to increase the speed at which machines operate which has required the development of new techniques for handling the signatures at all stages of a binding process.
Unfortunately, there have sometimes been serious problems at a particular stage of the binding process. Specifically, it is well known that oftentimes it is difficult if not impossible to open signatures before they are dropped onto the gathering chain. This, of course, either results in incomplete collections of gathered signatures which must be rejected at or before the stitcher or results in a chokeup that can shut down a bindery line thereby seriously decreasing plant efficiency with a resultant increase in costs. Normally, it follows that the high volume presently produced by the U.S. printing industry cannot then be maintained and the most efficient possible use of manpower, equipment and plant space is then not made. Presently, it is well known that unopened signatures are principally caused by two different problems.
First, static is known to be a problem in bindery lines. While this is normally a problem in the press room, it can also be a significant source of difficulty in a binder line since the presence of static tends to keep the signatures closed despite the existence of grippers that are designed to open the signatures immediately before they are dropped to the gathering chain. If unopened, the signatures cannot straddle the gathering chain and will simply fall out onto the floor.
In a typical bindery line, there may be on the order of twenty-four packer boxes in operation in the line. Thus, if static is a problem, any one or more of the packer boxes may be subject to chokeup at any given time or, alternatively, signatures will be missing from what should be a complete collection of gathered signatures at the stitcher and this is a particularly serious problem when it occurs at random along the bindery line. Clearly, the grippers that have been utilized to open signatures have not successfully overcome this problem.
Second, there is the problem of dealing with pinholes in signatures to be opened. Specifically, it is known that the impaling pins used on signature folding devices can rivet signatures shut usually along the foot of the signature particularly when the impaling pins have been bent or are dull. When this occurs, conventional grippers have been highly unsatisfactory for opening signatures.
In essence, conventional grippers have had neither the reach nor the action that is needed to deal with static or pinholes. It has, thus, remained to improve apparatus design for opening signatures to be dropped so as to successively straddle the gathering chain. Accordingly, the present invention has as its principal object to successfully provide for improved signature opening.